Friday, March 4, 2011


                                                 CHEMICAL    SNOWFALL
This Fascinating experiment is based on the sublimation property shown by Benzoic acid.
·         A glass rectangular chamber
·         Sand or mud
·         Tripod  stand
·         Spirit lamp
·         Wire gauge
·         China dish
·         Benzoic acid
·         Some green plants with leafy branches and toy huts
Take  a glass rectangular chamber with wooden base. You can construct it by fixing the four glass walls and glass ceiling on the wooden base. Leave some space between any two edges while joining them together so that air can circulate well inside the glass chamber facilitating the burning of benzoic acid. Now spread a thick layer of wet sand or mud over the wooden base to give the appearance of land. Now place a tripod stand with a spirit lamp below it at one corner inside the chamber. Place wire gauge over the tripod stand and put a china dish over it it containing some benzoic acid.
Now insert the green plants or leafy branches here and there into the thick layer of sand inside the chamber giving the appearance of natural location of snowfall. You can also place some small wooden huts or toys over which the snowflakes of Benzoic acid will settle down to give the realistic view of snowfall.
Now put the flame on at spirit lamp and observe the shining white Benzoic acid crystals directly going into the vapour state .
As these vapours of Benzoic acid fall and touch here and there inside the chamber, they soon get solidified giving the appearance of snowfall over the things inside the chamber. As this sublimation process will speed up, the more dense snowfall will come into the view.                                                
                                                                                                                                                                             pictorial representation of chemical snowfall

              CHEMICAL   HARMONIUM ( Singing flame )
This  experiment is based on the fact that when a flame, as of hydrogen gas or coal gas , burning within a tube is adjusted in such a way so as to set the air within the tube in vibration , it causes sound with different notes with changing  levels of air column inside the tube.
Take some pieces of granulated zinc and put them into Woulfe’s bottle. Now add some dilute Sulphuric acid to this bottle using thistle funnel . Soon the hydrogen gas will start coming out of the delivery tube. Now ignite the hydrogen gas with the help of match stick .
The hydrogen gas will start burning with a blue flame. Now surround this flame with a glass tube about half an inch in diameter with both ends open. Now move the glass tube vertically up and down. A musical sound will be produced. You can set a musical tone just like harmonium d, by continuously moving the glass tube vertically up and down along the flame.
                                                CHEMICAL  SUNSET

 Take two convex lenses and fix them in front of a light source in such a way so that a bright spot of light is obtained on the screen placed in the straight line just after the lenses. Place the entire setup in dark to visualize the effect. Now prepare 10% Sodium thiosulphate solution ( hypo solution ) by dissolving approximately 70 gm in 400 ml of distilled water and fill it in a beaker. Now place this beaker in between the two lenses . Make sure that the light source, two lenses, beaker and the screen should all be in a straight line.

Now add a little dilute hydrochloric acid to the hypo solution placed in beaker. The bright lighted spot on the screen getting cloudy and finally disappears after sometime. This gives the impression of a setting sun. This is what we called chemical sunset.
Mechanism behind this phenomenon :
Diagramatic demonstration of chemical sunset

Picture demonstration of chemical sunset

The above observation occurred due to the precipitation of sulphur from sodium thiosulphate, which makes the solution opaque and light can not pass through.